[libstdc++] Quote LD_RUN_PATH properly

[Neil Booth]

Phil Edwards wrote:-

> Neil noticed that BSD make was failing to build abi_check, with an error
> message involving "+".  Turns out things weren't being expanded properly.
> Fixed thusly.  Reproduced on i686/linux using pmake 1.45, and tested the
> same way.  Applied to trunk, queued for 3.3.1.

Thanks Phil!  I'll let you know how it goes next time I bootstrap.

Neil.